Means for automatically copying pictures and making printing plates for printing pictures, etc.



Nov. 25, 1930. H. DREWELL 1,732,717 MEANS FOR AUTOMATICALLY COPYING PICTURES AND MAKING PRINTING PLATES FOR PRINTING PICTURES, ETC

Filed Sept. 4, 1928 4 Sheets-Sheet I H. DREWELL MEANS FOR AUTOMATICALLY COPYING PICTURES AND MAXI PRINTING PLATES FOR PRINTING PICTURES, ETC

- Filed Sept. 4, 1928 4 Sheets-Sheet 2 Nov. 25, 1930.

Nov. 25, 1930. H. DREVIIELL MEANS FOR AUTOMATICALLY COPYING PICTURES AND MAKING PRINTING PLATES FOR PRINTING PICTURES, ETC

Filed Sept. 4, 1928 4 Sheets-Sheet 5 H. DREWELL MEANS FOR AUTOMATICALLY COPYING PICTURES AND MAKING Nov. 25, 1930.

PRINTING PLATES FOR PRINTING PICTURES, ETC

Filed Sept; 4, 1928' 4 Sheets-Sheet 4 Patented Nov. 25, 1930 PATENT OFFICE HEINRICH DREWELL, F IBERLIN-CHARLOTTENBURG, GERMANY MEANS FOR AUTOMATICALLY COPYING PICTURES ANn MAKING PRINTING PLATES FQR.

PRINTING PIcTUREs, ETC.

Application filed September 4, 1928, Serial .No. 303,765, and in. Germany April 3,1926.

For printing pictures containing halftones it is necessary to break up the surface of the picture to small parts which generally are separated from one another each making when printing a single dot on the printing paper. In the bright parts of the printed picture these dots are small compared. to their distance leaving a free space between them whilst in the shady parts the dots are o larger and coherent with the surrounding dots leaving no free space in the darkest parts.

The breaking-up of the printing surface is heretofore generally obtained by making'a 5 photograph of the picture to be printed and thereby inserting in the way of the light close to the sensible photographic plate or sheet a screen of crossed lines thus making a socalled half-tone picture. The latter is then transferred by means of a further photographical process to a metal plate commonly a zink-plate coated with a film of chromated gelatine. Finally the metal plate is prepared for printing by a suitable etching process. This photographical way of making half-tone pictures requires much experience and an expense of time which is especially undesirable when making printing-plates for printing news-papers.

My invention consists in'a device for automatically transferring a copy from a photograph or any similar picture as an original to any drawing or printing surface which may be the surface of a metal-plate or a sheet of paper or the like, each point of the original being singlytransferred and the copy being composed by single dots or impressions of different size. When working on a metal plate provided with asuitable skin of lac, varnish or any medium adapted to resist.-an etching fluid, the skin is simultaneously erforated in such a way that the etching uid is enabled to enlarge and to deepen the impressions on the metal surface according to their different size in which they are transferred to -the plate thereby preparing it to be printed from. To obtain this effect I pro- I vide an oscillating member forming a needle or pencil preferably made of hardened steel which may be designed in the following as a lamp and a system of lenses are arranged so that its light passes through asmall part of the transparent original picture and then gets into the photo-electric device, whereby the intensity of light which is allowed to act on the photo-electric device depends upon the degree of brightness or blackness ofthe particulltr part of the original picture.

The action of the photo-electric device depends upon' the quantity of light getting into it and further on the oscillations of said printing-pencil and its impressions on the printing surface depend upon the operation of the photo-electric device and therefore also upon the degree of blackness of a certain part of the original picture.

Moreover my invention may be used for making copies from an original picture on a sheet of paper or any similar substance in the black-and-White manner or in any desired colour. For this purpose the printing-pencil is arranged to oscillate transversely through a small receptacle or box filled with a-suitable ink and having its walls suitably perforated and provided with nozzles to allow the printing-pencil to pass and to take with it a certain quantity of ink transferring it to the surface of the printing sheet. If litho graphic ink is used in this case, the obtained copy may be used as a printing original to print from by a lithographic transferring process or by an olfset-printing'process.

Except for printing copies may be made by the apparatus for any other purpose. As

-it is possible to transfer ink of any desired so J printing surface, copies showing the objects in natural colours may be obtained.

If the desired copy is to be made from a non-transparent original picture, a system of lenses is provided before this picture and the light of a lamp is directed by means of suitably arranged mirrors through a part of the lenses as to illuminate a small part of the original picture. From this the light is diffusely reflected and partly gets into another part of the system of lenses and further on into the photo-electric device by means of which it will control the action of the oscillating printing-pencil as before mentioned.

The photo-electric device which serves to accommodate the oscillations of the printing-pencil to the degree of brightness or blackness of the original picture comprises as an essential member a so-called photoelectric cell.

Two kinds of photo-electric devices are known and may be employed to carry out my invention into practice. One of these is a resistance of selenium arranged to present a large surface to the light which will when touching this surface diminish the resistance of the selenium and cause an electric current which circulates therein to increase.

Another sort of photo-electric device is the so-called photo-electric cell and consists of an evacuated vessel or tube of glass the interior surface of which is partly coated with a skin of an alkaline metal, preferably potassium, and has a ring-shaped anode of some other metal. The skin of potassium is used as a cathode. If the anode and the cathode are connected to the corresponding poles of a source of electric current and a certain quantity of light enters the cell and touches the cathode-skin an electric current will be produced corresponding exactly to the quantity of the light.

For the sake of more surety and exactness in operation I prefer to employ this photoelectric cell but the present invention may also be carried out with the selenium-resistance.

The printing-pencil is caused to oscillate' by means of an alternating electric current. When oscillating the pointed end of the printing-pencil strikes against a drawing or printing-surface which may be the surface of a metal plate or of a sheet of paper or any other suitable material. All the points of the printing surfaces are to be presented one after another to the printing-pencil and correspondingly the points of the original picture must be brought into position as to control the light acting on the photo-electric cell. For this purpose I provide two slides the one of which is movable to and fro in a guide mounted on the other slide. The latter is moved stepwise in a direction rectangularnto that of the to-and-fro movement of the first slide. This slide serves as a common carrier of both the original picture and the printing-surface. Plates of glass carrying the original picture and plates of metal to be printed on may be fixed on the slide by suitable clamping means; sheets of paper or similar material carrying the original picture or to be printed on may be pasted after being moistened with their edges on the corresponding parts of the slide and after becoming dry will present a plane surface to the light controlled electric device and to the printing-pencil. The movements of the slides are brought aboutautomatically by suitable driving means. During a to-andfro movement of the first slide the printingpencil makes a line of impressions on the surface corresponding to a line drawn across the original picture. After one line of impressions has been finished, the other slide is moved a step forward and then the first slide continues its movement in the opposite direction whilst the printing-pencil makes a further line of impressions or dots on the printing surface near to the former line.

In order that the invention may be clearly understood reference is made to the accompanying drawings in which one embodiment of th'e device with its essentialdetails is represented diagrammatically by way of example, and in which Figure 1 shows the mechanism of the apparatus in a front-view, Figure 1 is a detail, Figure 2 a top-view, Figure 3 is a diagram of the electrical connections, Figures 4 and 5 show the device for producing the alternating current, Figure '6 a detail of the 1 device shown in Figs. 4 and 5; Figure 7 represents diagrammatically another form of the light-controlled electric device for making copies from a non-transparent picture, Figure 8 shows a side-elevation of the printing-device with some parts in section and Figure 9 a front-elevation of the same de-. vice, Figure 10 is a front-view of the ink-- box and its support, Figure 11 shows a crosssection of the nozzle surrounding the printing-pencil and Figure 12 is a detail view of the printing-pencil.

The original picture 1 and the printing sheet 2 (Figs. 1 and 2) are suitably fastened on the horizontal slide 3. The printing sheet 2 may consist of paper, metal or some other material. In the arrangement represented in Figs. 1 and 2 the original picture 1 is supposed to be transparent, i. e. a photographic negative or diapositive.

The light of an electric lamp 4 is directed through a small part of the original picture 1 by means of lenses 5. The lamp 4 and the lenses 5 are adjusted in such a way that an a image of the incandescent thread of the lamp minated part of the original is projected in the film-surface of the origi nal picture. The incandescent thread is preferably wound up in the shape of a helix of equal length and width with its turns-closely together and having its axis parallel to the surface of the original picture. In'this case the image of the thread of the lamp 4 will be projected in the shape of a small approximately square spotand almost equably illuminate a corresponding small part of the picture. A further lens 6 is mounted in the tube 7 extending from the wall of a case 8'opposite' to the front-side of the original picture. This case 8 encloses a photo-electric cell 9, preferably a potassium cell. The light passing through the original picture 1 and falling upon the lens 6 is concentrated by the latter and conducted into the photo-electric cell 9-. Owing to the degree of blackness of the illupicture a certain v part of the light passing through it is abvessel of sorbed and does not influence the photo-elec- 'tric cell 9. This cell consists of a tube or glass and has a cathode 11 forming a thin cover on the interior side of the tube. The cathode 11 is connected with the negative pole of the battery 57 (Fig. 3) and the anode 10 of the photo-electric cell 9 is connected with the positive pole of a section of the battery 57.

The action of the light coming to the cathode 11 causes an electric current proportional to the quantity of light falling into the cell. The lamp 4 and the lenses 5'are mounted on the top-plate 119 of the main frame of the apparatus. A support 121 rests upon the same top-plate and is rotatably secured by a neck-screw and maybe adjusted in the proper distance opposite to the original picture by meansof an adjusting-screw 122 acting against the pressure of a leaf-spring 123. The lenses 5 too can be made adjustable in a similar manner. i

The amplifying device is shown diagrammatically'only in Figure 3. The anode 10 of the photo-electric cell 9 is connected with the positive pole of a section of the battery 57, the negative pole of which is connected with its cathode 11 and through agrid-resistance 12 and a battery 13 with the grid 15 of an amplifying tube 14. The filament 16 of the amplifying tube 14 is heated by means of a 7 battery 16 and is also connected with the negative pole of the battery ,57. The anode an oscillatory circuit 17 of the tube 14 is connected with the positive pole of the battery 57 over a resistance 18 and a self-induction coil 19, From the end of the resistance 18 a further connection leads to the grid-battery 20 and then to the grid 21 of the amplifying tube 22, the filament of which is connected tion coil 19 and is heated by the battery 24; it is further connected to the positive pole of battery 57 and to the negative pole of the battery 58. The potential of the grid 21 and consequently the anode current of the amplifyingtube 22 depends upon the voltage of the grid battery 20 and the voltage drop caused in the resistance 18 and the self-induction coil 19 by the anode current of the amplifying tube 15.

Owing to the well-known effect of self-inductance an additional voltage drop besides the ohmic voltage drop in the self-induction coil 19 is produced during any time when the anode current of the amplifying tube 15 increases i. e. when the intensity of the light acting on the photo-electric cell 9 increases; and vice versa when the intensity of light and consequently the anode current of the tube 15 is diminished the self-inductance causestemporarily an enlarged diminution of the voltage drop on the self-induction coil 19 and of the potential of the grid 20. The effect hereof is that the fluctuations of the light which acts on the photo-electric cell 9 and of the anode current of the amplifying tube 15 cause temporarily enlarged fluctuations of the anode current of the amplifying tube 22.

The purpose of this arrangement is to overcome the inertia of the oscillating printingpencil and to instantly accommodate its oscillations to the intensity of light when changing.

From the positive-pole of the battery 58 there is a connection through the resistance 27 to the anode 25 of the amplifying tube 22. From one end of the resistance 27 a connection leads over the secondary coil 29 of a transformer 29 and 30 and'a grid battery 28 to the grid 31 of a further tube '32. The other end of the resistance 27 is connected with the filament 33 of the tube 32. A bat tery 34 supplies the current for heating this filament. The latter is also connected w th the negative pole of a battery 59, the positive pole of which is connected wlth the anode 35.0f the tube 32 over'the primary coil 37 of the transformer 37, 38.

In the circuit of the secondary coil 38 of this transformer thereis inserted theoscillating string 82 of the printing-device. To the primary coil 37 there is connected in parallel a condenser 39 forming with said coil the frequency of which is adapted to the frequency of the alternating current that keeps the string 82 oscillating."

The grid 31 of the amplifying tube 32 is controlled simultaneously by the anode-curto the self-induc-' rent of amplifying tube 22 circulating in the resistance 27 and by the alternating current circulating in the transformer 29, 30. The influences of both currents being superposed the tube 32 may be designated in the following as the superposition tube.

. The alternating current for energizing the transformer 29, 30 may be derived from any suitable source of alternating current. But to obtain a well defined and constant frequency and amplitude of this current I prefer to produce this current by means of an oscillating leaf-spring 46 controlling the grid potential of an amplifying tube which may be designated as the generator tube, in the following manner.

Referring first to the diagram shown in Fig. 3 a leaf'spring 46 is arranged to touch when oscillating alternately two contactscrews 47 and 48. .The contactscrew 47 is connected likewise to the negative pole of the battery 59 and to the filament 42 of the generator tube 41. The filament 42 is heated by the current from the battery 34. The contact-screw 48 is connected across a resistance 49 preventing short circuit to a small section of the battery 59, whilst from a larger section of the same battery a connection leads to the primary coil 30 of the transformer 29, 30,

further on to the primary coil 54 of the transformer 54, and at last to the anode 43 of the generator tube 41. The leaf-spring 46 is electrically connected across a grid battery 45 to the grid 44 of the tube 41. Two coils and 66 (Figs. 4 and 5) are connected to the secondary coil 55 of the transformer 54, 55 to be energized therefrom.

When the leaf-spring 46 comes in connection with the contact-screw 47 the potential of the grid 44 of the generator tube 41 is depressed by the grid battery so far in the negative that the anode current of the tube is prevented from circulating. Otherwise when the contact screw 48 is touched by" the leafspring 46 the grid potential is raised because the positive voltage of the small section of the battery 59 overcomes the negative voltage of the grid battery 45 and the anode current of the tube 41 is caused to circulate. Owing to the oscillations of the leaf-spring 46 an intermittent current is produced and circulates in coil 30 and 54 of the transformers 29, 30 and 54, 55 respectively.

Consequently an alternating potential is roduced in the coil 29 which acts on the grid 31 of the superposition tube 32 as described before. An alternating current is further produced in the coil 55 which magnetizes the cores 62 and 63 of an electromagnet by means of the coils 65 and 66. This electromagnet keeps the leaf-spring 46 oscillating and its arrangement is more particularly shown in Figs. 4 and 5. llhe electromagnet comprises three cores 61, 62 and 63, which are surrounded by the coils 64, 65 and 66.

The cores 62 and 63 consist of iron-blades and are mounted on the top end of a yoke 61 in the lower part of which is introduced one end of the core 61. The other end of this core rests in a pillar 69. The leaf-spring 46 is fixed on the upper part of this pillar, its free end being opposite to the poles 67 and 68 of the cores 62 and 63 respectivel tongue 70 is cut out from the lea spring and is connected with the latter only on its basis in such a way that it strives to partake in the oscillationsof the leaf-spring 46. The tongue 70 is provided with two small contact plates 71 and 72 opposite to the contact-screws 47 and 48 and alternately touching the same when the leaf-spring oscillates. In Fig. 4 the contact screw 48 has been omitted to give a better view of the tongue 70. Two small iron-pieces 46 are riveted on the free end of the leaf-spring 46 to increase the action of the magnetic power of the poles 67 and 68 on the leaf-spring 46. The oscillation of the latter is to a certain degree independent of that of the tongue 70 the movement of which is limited by the contact screws 47 and 48, a sufficient durance and regularity of the contacts being obtained in this way. Further to obtain a most regular oscillation of the leafspring 46 the poles 67 and 68 may be provided with wave-shaped edges leaving a corresponding small crevice between them as particularly shown in Fig. 6. The core 61 and consequently the leaf-spring 46 are magnetized by a direct current circulating in the coil 64.

When the operation is started the oscillations of the leaf-spring 46 have to be initiated, f. i. by hand. It then keeps oscillating by the alternating current which is produced in the following manner.

Whenever the leaf-spring swings in the direction of the pole 67 the. contact 71 touches the screw 47. This brings about a negative potential to the grid 44 of the tube 41 against the filament and the anode-current in the tube 41 is interrupted. This causes by way of induction a current in the secondary coil 54 of the transformer 54, 55 in such direction as to magnetize the two magnets 62 and 63 so that the free end of the leaf-spring 46 be attracted more intensely by the pole 68 and swings up to the latter. This causes the contact plate 71 to leavethe screw 47 and the contact-plate 72 to touch the screw 48. Now the voltage of the section of the battery 59 connected with the screw 48 overcomes the voltage of the grid-battery and gives the grid 44 a positive potential. Owing to this the anode-current in the generator-tube 41 starts again and a current induced in the transformer 54, 55 in the opposite direction causes the plate-spring 46 to swing back to the pole 67. This actionis repeated as long as the generator-tube 41 is provided with electric power from the battery 59. The intermittent A small j direct current in the anode circuit of the generator tube 41 is changed into an almost sineshaped intermittent direct current by means of a condenser 50 (Fig. 3), switched in parallel to the' coils 30 and 54 and forming therewith an oscillatory circuit which is turned to the frequency of the oscillations of-the leafspring 46.

The device here described for producing an alternating current is not an essential part of the present invention; the alternating current may as well be derived by some ordinary electric power-supply if available.

Such current may have a very low frequency and will require the use of a frequency-transformer. Furthermore the ordinary fluctuations of voltage in a public powersupply have to be annihilated by suitable means, f. i. by iron-resistances. Instead of batteries there may be used any othermeans for producing direct electric current, f. i. rectifiers that are fed with an alternating current of constant Voltage.

The printing-pencil 81 is suitably fastened (see Figs. 1, 2, 8-, 9 and 10) in the middle of a string 82. This string consists of a band of a non-magnetic but electrically conducting material, for instance bronze, and is stretched between a lever arm 84 and a lever 85 in such a way that it may oscillate freely in the gap 86 between the poles 87 88 and 89, 90 of an electromagnet 100. The oscillations are obtained by the co-action of the,

alternating current in the string 82 and the magnetic power of the electromagnet 100 in a direction rectangular to that of the oscillating string 82 and to the direction of the magnetic power i. 'e. in the direction of the printing-pencil 81.' The band-shape of the string will prevent oscillations in another direction. To avoid rotary oscillation of the string 82 the printing-pencil 81 is provided with a rod 91 that is guided in the slit 92 of a plate 93. Into a gap 94 of the latter engages the flange 95 of a screw 96 which allows to adjust the plate 93 in a vertical direction. =The electromagnet 100 has a gap 102 which leaves a free passage to the rod 91 when swinging backwards. The, right end of the string 82 is fixed to a suitable pin 104 on the-arm 103 of a three-armed lever 84, 103, 105 (Fig. 2) which is rotatably mounted on the plate 117. 1

The arm 1 05 of this three armed lever is pressed against an adjusting-screw 106 by means of the tension of the string 82 acting on the lever arm 84. The left endof the string 82 is fixed on a pin 107 on the lever 85. The lever 85 is rotatably held by a-neckscrew 108. A leaf-spring 109, pressing with its one end against the lever 85, is bent round a neck-screw 110 and rests with its other end against an adjusting-screw 111, which bends the leaf-spring 109 thereby'tightening the string 82. The ends of the string 82 are by means of slightly movable metal cords 115.

The screws 116 are fastened on the edges of the base-plate 117 (Figs. 1, 2 and 9). The latter carries on its surface the levers 84 and 85 and is supported by pillars 118' on the frame 120 (Fig. 9). Like the frame 121 of the controlling device the frame 120 is pivoted upon the base-plate 119. A screw 125 against which an arm 126 of the frame 121 is pressed by, a leaf-spring 127 is provided for the adjustment of .the proper distance between the printing-pencil 81 and the printing surface 2. a

r In case the copy is to be made with lithographic ink or some other liquid colour the printing-pencil 81 may be supplied with the ink or colour in the following manner (see Figs. 8 and 9). A small receptacle 140 designated in the following as the ink box is provided between the poles of the electromagnet 100 and the printing surface 2.. The

printing-pencil 81 oscillates without touching their edges whilst the ink or colour is prevented from flowing out of the ink box by the capillarity.

The ink box 140 is removably fastened on a support 149 by means of .a neck-screw 144 which engages in a recess 145 of the holder 146 of the ink box 140. A leaf spring 147 presses with. its one end a projecting edge in the opening 145 against the neck of the neck screw 144. After pressing down the spring the ink box can be removed. The other end of the spring 147 presses the holder 146 against the adjusting screw. 148. By means of this screw the holder 146 can be turned around the screw 144 as a pivot thereby adjusting the ink box 140 in a higher or lower position. The screw 144, the spring 147 and the adjusting screw 148 are mounted on the support 149 which with its upper hor1- zontal part glides upon the horizontal part of the pole 87 of the electromagnet 100 on which' it is adjustably secured by a guide 150 engaging in a slit of the support 149. The guide150 possesses a projiecting lug 151 serving as a nut for the a usting screw 153. On. its enlarged neck this screw has a groove 154 with which gears the forkshaped vertical end 152 of the support 149. With the aid' of theadjusting'screw 153 at the distance between the ink box 140 and the printing-surface is adjusted and the polnt of theprinting-pencil 81 is made to d1ve when oscillating more or less into the ink in the nozzle 141 whereby the supply of the nk is regulated simultaneously.

Figs. 11 and 12 show a particul cal form of the printing-pencil; view in the direction of the movement of the slide 3. Fig. 12 a view in a direction recrl practi- Fig. 11 a tangular to the former one. Here the point of the printing-pencil has the form of a small hatchet.

When striking against the printing surface it produces longer or shorter but very small dashes across the line of impressions caused by the movement of the slide 3. These dashes extend into the space ofthe lines printed before and afterwards and in consequence the single lines melt into one another even when the copy has been printed with a coarse grain.

Instead of applying a liquid coloring matter or ink a sheet of so-called carbon-paper may be put upon the printingsurface and by this means a coloured copy may be produced according to the impacts of the printing pencil 81. This process may be of some importance for instance for certain printing machines that use a so-called offset-printing process with aluminium sheets or such like. Printing with the colour from the carbon paper which contains fat and wax, produces upon the aluminium sheet a transferable copy just as if the sheet is written upon with a typewriter with carbon paper.

A combination of two slides 3 and 158 is provided for the purpose of guiding every point of the printing surface one after another to the position to be touched by the printing-pencil 81 and to simultaneously guiding the corresponding points of the original picture into the way of the light passing from the lamp 4 into the photo-electric cell 9.

The common carrier of the original picture 1 and the printing surface 2 represents the one slide 3 which glides in a guide 157 and is horizontally movable therein; The guide 157 is mounted on another slide 158 which is adapted to glide in a vertical guide 159. The horizontal movement of slide 3 is a rapid to-and-fro movement and each time when its direction is changed the slide 3 is elevated a small distance.

Thus the printing pencil 81 makes a line of dots on the prlnting surface during a movement of the slide 3 in the one direction and during the following movement in the opposite direction another line'of dots which is placed a small distance below the first line according to the elevation of slides 3 and 158.

The to-and-fro movement of the slide 3 and the stepwise vertical movement of the slide 158 are brought about in the following manner: An electric motor 180 carries on the one end of its axle a friction disk 181 which rotates between two further friction disks 182 and 183 and is adopted to touch and to drive alternately one. of these disks. The friction disks 182 and 183 are fixed on a hollow shaft 184 the lowerend of which is guided in a bearing 185 and supported by a bearing block 186. The latter rests on an eccentric drum 187 fastened on a rotatable shaft 188. By turning the eccentric drum 187 the bearing block 186 and the shaft 184 with the friction disks 182 and 183 may be elevated or sunk. In the lower position of the shaft and then together with the shaft 184 rotated in the opposite direction. The action of the weight of the shaft 184 and the disks 182 and 183 when touching the disk 181 in their lower position may be supported by a suitable spring. Also the bearing block 186 may be divided into two parts and a suitable spring may be inserted between the same to obtain a yielding pressureof the disk 183 against the disk 181.

In the hollow shaft 184 there glides a shaft 189 the upper end of which is guided in the arm 190 which extends from the guide 157 of the horizontal slide 3. The upper end of the shaft'189 carries a conical gear wheel 191 which engages into another conical wheel 192 on the end of a screw or spindle 193. A nut-screw not shown in the rawings engages into the screw 193 and is fastened to the back side of the slide 3. When turning the screw or spindle 193 in a certain direction the slide 3 is moved in a corresponding direction.

A pulley 195 is mounted to rotate freely but not axially displaceable on the shaft 188 and is continuously driven by another pulley 196 fixed on the end of the axle of the electric motor 180. With the pulley 195 there is connected a crown wheel 197 provided with ratchet teeth. A coupling-pawl 198 on the arm 198 (Figs. 1 and 1) of a twoarmed lever 198, 199 is adapted to engage the ratchet teeth of the crown wheel 197. The lever 198, 199 is pivoted on a sleeve 201 which is fixed on the shaft 188 opposite to crown wheel 197 and is pivoted with a finger 212. The latter supports a spring 211 which strives to press the coupling pawl 198 into the teeth of the crown wheel 197. The pivots 200 of the lever 198, 199 are in right angles to the axis of the shaft 188. A forksha e'd lever 202 secured on the lower end of a s aft 205 is provided with two inclined faces 203 and 204 which extend into the way of the arm 199 of the rotating lever 198, 199

in such manner that they will press against the arm 199 and turn the lever 198, 199 as to withdraw the.other arm 198 and its coupling pgyvl 198 from the teeth of the crown wheel When the coupling pawl 198 is removed from the teeth of the crown wheel 197, the arm 199 of the lever 198, 199 abuts against one of the stops 203 or 204 and stops the rotation of the shaft 188. On the middle part of the slide 3 there are provided two ad ustable stops 208jand: 209 which may be pressions to be made close below the former fixed by screws 210 in channel or groove 211. A plate-shaped lever 207 (Figs.,/1 and 2) is fastened to the upper, end ofthe shaft 205 and extends in the way of the stops 208 and 209 in any elevated position of the slides 3 and 158. v 1

When starting the devicefrom the position shown in the drawings (Figs. 1, 1 and '2) the slide 3 will move from the left to the right in Fig. 1. Then after a short time the stop 208 abuts against the lever 207 and turns the shaft 205 by a small angle. Thereby the lever 202 on the lower end of the shaft 207 comes from its former position into the position shown in dotted lines in Fig. 1. The arm 199 of the lever 198, 199 leaves the face 203 and allows the arm 198 to engage with its pawl 198 into the teeth of the crown wheel 197. Thus the lever 198, 199 the sleeve 201 and the shaft 188 are forced to partake in the rotation of the pulley 195. Having made nearly half a revolution the arm 199 glides on theother inclined face 204 whereby thecoupling pawl 198 is removed from the crown wheel 197 and the rotation of shaft188 is stopped again by the lever 199 abutting against the stop 204". In this way each movement of the shaft 205 causes half a revolution of the shaft 188 and brings simultaneously the eccentric 187 in a position opposite to the former one.

This causes the positions of the shaft 184 and the disks 182 and 183 to be changed and its rotation to be turned into an opposite direction. Thereby the movement of the slide 3 is also turned into the opposite direction.

The rotation of the shaft 188 is transferred by the conical gear-wheels 214, 215, the shaft 216, further conical gear-wheels 217, 218 to a shaft 219. This shaft carries a worm 220 which engages a worm-wheel 221. The latter is fixed on the lower end of a spindle 222 which serves for stepwise elevating the slide 158. The spindle 222 is provided with a collar 223 which rests in a recess of the bearing block 224 thus supporting the spindle 222.

A nut-screw not shown in the drawings is fastened to the back side of the slide 158 and engages the spindle. 222 turning its revolutions into a straight movement of the slide 158; Every time the shaft 188 makes half a revolution that is when the direction of the movement of the slide 3 is changed the slide 158 iselevated by turning the screw 222, thus causing the following line of imone.

Another arrangement of the photo-electric controlling device is shown diagrammatically in Fig. 7. This arrangement may be used in case copies are to be made from a picture in the place of the photo-electric controlling device shown in Figs. 1 and 2. In Fig. 7 the lamp 4 is mounted above the photo-electric cell 9 and its light is reflected by a mirror 131 and. after passing a lens 132, again reflected by a second mirror 133, thus coming to the upper part of a system of lenses 134.

Then it is concentrated to intensively illuminate a very small part of the original picture from which it is diffusely reflected. A part of this diffusely reflected light gets into the lower part of the lens-system 134 and after passing it to a mirror 135 and a further mirror 136. The latter reflects the light to a gap or diaphragm 137 in the front wall 138 of a case 8 of the photo-electric cell 9*. In order to exactly limit that portion of the original picture the reflected light of which acts on the photo-electric cell 9 the lens-system 13.4 is adjusted in such a distance before the surface of the original picture, thatan enlarged image of its illuminated part is projected by the lens-system 134 exactly in the plane of the gap or diaphragm 137. In this case only the light which passes the diaphragm 137 can get into the photo-electric cell and the part of the original picture from which this light is coming is exactly deter- -mined and limited by the edges of the diaphragm 137. The enlargement of the image projected in the diaphragm 137 may be of such a size that owing to the corresponding size of the diaphragm 137 diffraction of light on the edges of the diaphragm 137 will have no influence on the precise action of the photoelectric cell. Otherwise the part of the orig inal, picture acting simultanenously on the photo-electric cell may be a very small one because diffraction can be avoided by employing a sufiicient' enlargement by the lenses 134'and a corresponding size of the diaphragm 137. For this reason a diaphragm similar to that shown diagrammatically in Fig. 7 may be also inserted in the way of the light before the photo-electric cell 9 when using the arrangement shown inFigs. 1 and 2 for copying a transparent original picture. In the arrangement shown in Fig. 7 totally reflecting prisms may be used instead of the mirrors 131, 133, 135 and 136.

For the sake of more clearness the operation of the complete apparatus may be described in the following.

The horizontal slide 3 is moved to and fro with an equal rapidity. Each time the direction of this movement is changed the slide 158 is elevated a small step. The rapidity of the movement of slide 3 and the size of the steps of slide158 depend upon the grain which is desired for the picture or copy to be produced. By the combined movements ofthe. slide 3 and the slide 158' all the points of the original picture are presented one after the other beforethe photo-electric cell 9 in the way of the light, issuing from the lamp 4 into said cell. A certain part of this light corresponding to the degree of transparence or brightness of the original picture in the presented point is allow to pass into the photoelectric cell 9. An electric current is produced in the cell, the intensity of which in every moment corresponds to the intensity of the light entering the cell 9. This electric current causes a potential difference on the resistance 12 in such way that the negative potential of the grid 15 of the amplifying tube 14 becomes elevated and even when a large intensity of light enters the cell 9 a positive potential of the grid may result. Owing to the elevated potential of the grid 15 the electric current in the anode-circuit of the amplifying tube 14 increases and produces an increased potential difierence at the ends of the resistance 18 and the self-induction coil 19 which are inserted in the anode-circuit of the amplifying tube 14.

The total difference of the potentials at the outer ends of the resistance 18 and the self-induction coil 19 controls the action of the following amplifying tube 22 in such way that the potential of the grid 21 is lowered and consequently the anode-current of the tube 22 is diminished. Besides this the increasing of the total difference of the 10- tentials on the outer ends of the resistance 18 and the coil 19 depends upon the rapidity with which the electric currents in the photoelectric cell 9 and in the amplifying tube 14 is increased or diminished and is corresponding to the rapidity of alteration in the quantity of light entering the photo-electric cell 9. When this quantity of light is altered the self-induction of the coil 19 produces for a short time an alteration of the difi'erence of the said potentials which is larger than that corresponding to the alteration of the light entering the cell 9. In this way the fluctuations of the light produce for a short time comparatively enlarged fluctuations of the electric current. The purpose hereof is to overcome the inertia of the oscillating string 82 and to immediately accommodate its oscillations to the intensity of light when changmg.

The anode-current of the amplifying tube.

22 causes 'a certain difference of the potentials at the ends of the resistance 27. This difference reaches its highest point when no light gets into the cell 9 and acts on the grid 31 of the superposition tube 32 together with the alternating potential difference on the secondary coil 29 of the transformer 29, 30.

In every moment the potential of the grid 31 is determined by the total difference of potential produced by the anode-current of the amplifying tube 22 on the resistance 27 and by the alternating current of the transformer 29, 30 in the secondary coil 29. The primary coil 30 of the transformer 29, 30 reby means of a battery 28 and the current in 'the resistance 27 and is kept so far in the negative compared with the potential of the filament 33 that the action of the alternating potential on the coil 29 allows only a small intensity of intermittent current to flow in the anode-circuit of the superposition tube 32. This will only be during a short time in each oscillation of the alternating potential, when the potential of grid 31 exceeds the lowest point which allows the anode-current to circulate. The intermittent current in the anode-circuit of superposition tube 32 passes the primary coil of the transformer 37 38 to the secondary coil 38 of which is connected the string 82 which carries the oscillating printing-pencil 81. In the coil 38 is induced an alternating current. The anode current in the amplifying tube 17 increases and the one in tube 22 is diminished. Likewise the potential difference on resistance 27 is diminished and thereby the depression of the potential of the grid 31.

In each oscillation of the alternating current the potential .of this grid will be more elevated above the point at which the anodecurrent in the superposition tube 32 will begin to circulate and consequently the intensity of the intermittent current in the superposition tube 32 will be increased. This causes an increased alternatingcurrent inthe coil 38 and in the string 82 the oscillation of which will become more energized. Thus the energy of the oscillations of the string 82 depends upon the quantity of light acting on the photo-electric cell 9. H

The printing-pencil 81 which is rigidly secured to the midst of the string 82 partakes in the oscillations of the string 82 and strikes thereby against the printing surface 2. Its impressions on this surface will be imperceptible as long as no light acts on the photoelectric cell 9 and they will grow stronger and visible according to the quantity of light getting into said cell.

To obtain a sufficient vigour of the 08011- lations of the string 82 and the pencil 81 it is preferable to adjust the tension of the string 82 by means of the adjusting screw 117 so that its free oscillation frequency is equal to the frequency of the alternating current. Otherwise a strong damping means must be provided on the string 82 to prevent disturbing oscillations produced by the impacts of the printin -pencil 81 against the printing surface. owever a certain degree of damping is always necessary to immediately accommodate the oscillations of the string 82 to the fluctuations of the light and a correspondinglloss of electric energy is connected therewit By employing the self-induction coil 19 in the grid-filament circuit of the amplifying tube'15 this loss of energy is diminished because the self-inductance causes an enlarged influence of the fluctuations of the light and consequently a quicker accommodation of the oscillations of the-string 82. Damping by air-resistance is in this case sufficient to secure an accurate operation of the printing-pencil 81. 1

The combination of two slides for bringing the original picture and the printing surface to their proper positions as required is not an essential feature of my invention and the slides may. be replaced by other means adapted to obtain the same purpose. For example, if flexible sheets or films are employed both for the original picture and for the printing surface these sheets or films may be fixed on drums. The to-and-fro movement of the slide 3 is then to be replaced by a rotation of the drums whilst, the stepwise movement of slide .158 is replaced by a slow axial displacement of the drums. Meansfor obtaining the required combination of movement in this Way are well known for example from devices for telegraphic transmission of:

photographs, or from phonographs, and similar apparatus and may be also employe'd'to carry out my invention into practice.

In the following claims I beg to define as a light-controlled electric device not only a photo-electric cell but any device adapted to accommodate an electric current to the-intensity of light acting on said device. Also I beg to define as a printing surface any surface of metal plate or sheet or of a sheet of paper many other matter which is adapted to receive a copy of any picture by means of impressions made on it with or without transferring ink or any colored matter to it.

What I claim is:

1. In means for automatically making copies from an original picture, the combination of light-controlled electric means adapted to be controlled by the light acting on them, an oscillating string carrying a printing member adapted to make impressions of different size on a printing surface theintensity of its oscillations. being controlled'by said light-controlled electric means, and means for bringing in succession all the points of an original picture one after another into position to control the light acting on said light-controlled electric means and for simultaneously presenting corresponding points ,of'a printing surface to said oscillating member to receive im ressions therefrom.

2. In means for ma 'ng automatically on it and to control an electric current, amplifying means to amplify the electric current controlled by said light-controlled electric device, an oscillating member adapted to oscillate and to make impressions of different size on a printing surface, oscillation producing means adapted to act on said oscillating member and cause it to oscillate, oscillation controllingmeans adapted to control the action of said oscillation producing means on said oscillating member and to be controlled by the amplified current of said amplifying means, and means for bringing all'points of an original picture one after another into' position for controlling the light acting on said light-controlled electric device and for simultaneously presenting corresponding points of a printing surface to said oscillating member to receive impressions therefrom.

3. In means for making automatically copies from an original picture t ft-combination of a light-controlled electric device adapted to be controlled by the light acting on it and to control an electric current, amplifying means comprising a series of amplifying tubes,.a plurality .of sources of electric currents and a plurality of resistances, and adapted to amplify the current controlled by said light-controlled electr'c device, a self adapted to be controlled by the light acting induction coil inserted in t e anode circuit oscillate, oscillation controlling means adapted to control the action of said oscillation producing means on said oscillating member and to be controlled by the amplified current of said amplifying means, and means for bringing all points of an original picture one after another into position for controlling the light acting on said light-controlled electric device and for simultaneously presenting corresponding points of a printing surface to said oscillating member to receive impressions therefrom. v

4. In means for making automatically copies from an original picture the combination of a light-controlled electric device arranged to receive light from a small art of an original picture and adapted to be controlled there y and to control an electric current, a plurality of amplifying tubes each having a filament, a grid and an anode and being adapted to amplify the current controlled by said li lit-controlled electric device, a plurality 0 sources of electric current inserted in the anode circuits of said amplifying tubes, a plurality of sources of electric voltage inserted in the rid-filament circuits of said amplifying tu es, a superposition 5 tube having a filament, a grid and anode, a source of direct current inserted in the anode circuit of said superposition tube, a source of alternating current, a transformer having a primary and a secondary winding, its prim mary winding being connected to said source of alternating current to be energized thereby and its secondary winding being inserted in the grid-filament circuit of said superposition tube, a resistance inserted in the anodecircuit of one of said amplifying tubes and simultaneously connected in series with the secondary winding of said transformer in the grid-filament circuit of said superposition tube thereby causing a superposition of the actions of the direct current amplified by said amplifying tubes and of the alternating current produced by said source of alternating current and causing an intermittent current to circulate in the anode circuit of the superposition tube and to increase and decrease according to the fluctuations of the light acting on said light-controlled electric device, an oscillating member adapted to oscillate by means of the intermittent current of said superposition tube and to make impressions of different size on a printing surface, and means for bringing all points of an original picture one after another into position to control the light acting on said light-controlled electric device and for simultaneously presenting corresponding points of a printing surface to said oscillating member to receive impressions therefrom.

5. In means for making automatically copies from an original picture, the combination of, a light-controlled electric device adapted to control an electric current, amplifying means for amplifying the electric current controlled by the light-controlled electric device,alamp, optical illuminating means for directing the light of said lamp to a small part of an original picture for illuminating the same, a diaphragm placed in the way of the light before said lightcontrolled electric device, optical projecting means for directing the light from the illuminated parts of the original picture to said light-controlled electric device thereby projecting an enlarged image of the illuminated part of the original picture in the plan of said diaphragm for the purpose of limiting the part of the original picture which controls the light acting on said light-controlled electric device, an oscillating member adapted to oscillate and to make impressions of different size on a printing surface, oscillation means on said oscillating member and being controlled by the amplified current of said amplifying means, and means for bringing all points of an original picture one after another into position to be illuminated by means of said optical illuminating means and to be projected by said optical projecting means and further for presenting simultaneously corresponding points of a printing surface to said oscillating member to receive impressions therefrom.

6. In means for making automatically copies from an original picture the combination'of a light-controlled electric device arranged to receive light coming from an 30 original picture and adapted to be controlled thereby and to control an electric current, amplifying means for amplifying the electric current controlled by said light-controlled electric device, anoscillating member adapt- 35 ed to oscillate and to make impressions of different size on a printing surface, oscillation producing means adapted to act on said oscillating member and cause it to oscillate, oscillation controlling means for controlling so the action of said oscillation producing means on said oscillating member and being controlled by the amplified current of said amplified current of said amplifying means, and oscillation tuning means for tuning the oscillations of said oscillating member to the frequency of the oscillations produced by said oscillation producing means, and means for bringing all points of an original picture one after another intoposition for controlling the light acting on said light-controlled election of a' light-controlled electric device adapted to be controlled by the light acting on it and to control an electric current, a Ito plurality of amplifying tubes each havlng a filament, a grid and an anode and amplifying the current controlled by said light-controlled electric device, a plurality of sources of electric current inserted in the anode cir- 31B cuit of said amplifying tubes, a superposition tube having a filament, a grid and an anode, a source of direct current inserted in the anode circuit of said superposition tube, a source of alternating current, a superposition transformer having a primary and a secondary winding, its primary winding being connectedto said source of alternating current to be energized therefrom and its secondary winding being inserted in the grid-filament circuit of said superposition tube, a resistance inserted in the anode circuit of one of said amplifying tubes and simultaneously connected in series with the secondary winding of said superposition transformer in the gridto circulatein the anode circuit of said superposition tube and to increase and decrease according to the fluctuations of the light acting on said light-controlled electric device, a string transformer having a primary and a secondary winding and its primary winding energized by the intermittent current in the anode circuit of said superposition tube, a magnet having a gap between its poles, a string stretched in the gap of said magnet and being switched in the circuit of the secondary winding of said string transformer and oscillated by the alternating current induced therein, a printing pencil fixed to said string and oscillating with-the samethereby adapted to make impressions of different size on a printing surface, tension adjusting means for adjusting the tension of said string for tuning its oscillations to the frequency of oscillations of the alternating current produced by said source of alternating current, and means for bringing all points of an original picture one after another into position to control the light acting on said light-controlling electric device and for simultaneously presenting corresponding points of a printing surface to said printing pencil to receive impressions therefrom.

8. In means for making automatically copies from an original picture the combination of a light-controlled electric device adapted to-be controlled ,by the light acting on it and to control an electric current, a receptacle to be filled with ink and having perforations in its opposite side walls, a printlight-controlled electric device, and means for bringing all points of an original picture in a position for controlling the light acting on said light-controlling electric device and simultaneously presenting corresponding points of a printing surface to said printing pencil to receive impressions therefrom.

9. In means for making automatically copies from an original picture the combination of alight-controlled electric device adapted to be controlled by the light acting on it and to control an electric current, a lamp,.

optical illuminating means for directing the light of said lamp to a small part of an original picture for illuminating the same, optical projecting means for directing the light from the illuminated part of an original picture to said light-controlled electric device, a plurality of amplifying tubes, each having a filament, a grid and an anode for amplifying the current controlled by the light-controlled electric device, a plurality of sources of electric current inserted in the anode circuit of said amplifying tubes, a plurality of sources of electric voltage inserted in the grid-filament circuits of said amplifying tubes,-a plurality of resistances for controlling the grid-potential of said amplifying tubes, a self-induction coil inserted in the anode circuit of one of said amplifying tubes and simultaneously inserted in the grid-filament circuit of another of said amplifying tubes, and producing an additional temporary amplification of the fluctuation of the electric current controlled by said light-controlled electric device, a superposition tube having a grid, a filament and an anode, a source of direct current inserted in the anode circuit of said superposition tube, a source of alternating current, a superposition transformer having a primary and a secondary winding its primary winding being connected to said source of alternating current to be energized therefrom and its secondary winding being inserted in the grid-filament circult of said superposition tube, a resistance inserted in the anode circuit of one of said amplifying tubes andsimultaneously connected in series with'the secondary winding, of said superposition transformer in the gridfilament circuit of said superposition tube thereby causing a co-operation of the current amplified by said amplifying means and of 'the alternating current produced by said source of alternating current and causing an intermittent current in the anode circuit of said superposition tube to circulate and to increase and decreaseaccording to the fluctuations of the current amplified by said amplifyin'g tubes, a string transformer having a primary and a secondary winding and its primarywinding energized by the intermittent current in the anode circuit of the supertuning its oscillations to the frequency of oscillations of the alternating current produced by said source of alternating current,

and means for bringing all points of an ori'ginal picture one after another into position to be illuminated by said optical illuminating means and to control the light acting onsaid light-controlled electric device and for simultaneously presenting corresponding points of a printing surface to said printing pencil to receive impressions therefrom.

10. In apparatus for making copies of pictures or the like, a reproducing system comprising a tuned oscillating string carrying an impression member, means supporting a blank adjacent said member, a vacuum tube oscillator generating current of substantially the frequency of the tuned string, a vacuum tube including in the plate circuit thereof means for supplying current to said oscillating string, circuit elements for impressing upon the input circuit of said second tube an alternating voltage derived from said oscillator, a source of current ln'said input system establishing a normal grid bias effective to reduce the plate current of said second tube to a value below that required to contact said member with said blank, and a resistance in said input circuit and adapted to be traversed by a control current, whereby the potential drop established across said resistance provides a variable grid bias superposed upon said normal grid bias.

11. In apparatus for making copies of a picture or the like, the combination with means for supporting the picture and a blank, a light-controlled electric device adaptedto be controlled by the light acting upon it, of an impression element adjacent said blank, a support for said element, said support being mechanically tuned to oscillate at a predetermined frequency, a source of alternating current of substantially the tuned frequency of said support, electrical means actuated by said source for oscillating said support and the impression element carried thereby, and means actuated by said light-controlled device for determining the magnitude of the alternating current delivered to said electrical means, whereby the magnitude of the oscillations of said impression member is determined by the light acting upon said lightcontrolled device.

In testimony whereof, I aflix my signature.

HEINRICH DREWELL. 

